1. Field of the Invention
The present invention relates to a solid electrolyte fuel cell.
2. Description of the Related Art
A solid electrolyte fuel cell directly converts chemical potential energy contained in fuel into electric energy by an electrochemical reaction.
FIG. 1 shows a minimum unit of the solid electrolyte fuel cell for generation of electric power. As shown in FIG. 1, the cell 1 comprises a generation section 2, charge collectors 3 and 4 between which the generation section 2 is inserted, and separators 5 and 6 between which the generation section 2 and charge collectors 3 and 4 are inserted. The generation section 2 is a three-layer film and comprises an air electrode 7, a solid electrolyte film 8 and a fuel electrode 9.
Lanthanum manganite (LaMnO.sub.3) has been used for the material of the air electrode 7, and yttria-stabilized zirconia (referred to as YSZ hereinafter) has been used for the material of the solid electrolyte film 8. A cermet prepared by mixing, for example, Ni with YSZ has been used for the material of the fuel electrode 9.
Lanthanum manganite (LaMnO.sub.3) has also been used for the charge collectors 3 at the air electrode side and Ni has been used for the charge collectors 4 at the fuel electrode side. Lanthanum chromite (LaCrO.sub.3) has been used for the material of the separators 5 and 6.
The conventional solid electrolyte film 8 of the solid electrolyte fuel cell 1 having the cell construction described above has a sufficient thickness so that the cell can endure the stress generated during operation or when the temperature is increased or decreased. This causes a problem in that the cell suffers a large potential drop during power generation, thereby resulting in a low generation performance.
In order to solve this problem, it has been proposed that the solid electrolyte film be reinforced by adding alumina (Al.sub.2 O.sub.3) into the solid electrolyte film while reducing its thickness. It is true that alumina enhances the mechanical strength of the solid electrolyte film, but alumina also increases the potential drop. As a result, the solid electrolyte film has a good mechanical strength but also has a large potential drop, or the solid electrolyte film has a lower potential drop, but also has less mechanical strength.